1. Field of the Invention
The present invention broadly relates to solvent extraction procedures and, more particularly, is concerned with a method and apparatus for quantitatively separating and isolating major to ultratrace levels of extractable ingredients in small quantity samples of various materials.
2. Description of the Prior Art
Solvent extraction is regularly carried out in laboratories by chemists as a conventional procedure in analytical separations wherein the extraordinary ability of certain solvents to quantitatively and preferentially remove one or more constituents or ingredients from a solution or solid material sample is exploited.
One type of laboratory apparatus for extracting organic materials from a sample of a solid matrix containing such organic materials is described and illustrated in U.S. Pat. No. 4,028,060 to Godsey. Through a repeated sequence of alternately heating and cooling opposite ends of the apparatus, the solvent is made to repeatedly pass through the sample until the solvent passing also through the permeable sample support is substantially clear indicating that substantially all of the organic material has been removed from the sample.
However, the apparatus of the aforesaid patent has several drawbacks. First, it takes technical skill to perform the steps of the procedure. Second, applications for the apparatus are limited in scope. Third, the apparatus requires auxiliary equipment, such as cooling and heating sources. Fourth, use of the apparatus with a solvent presents an explosion hazard since it is necessary to heat a portion of the sealed apparatus to approximately 100.degree. C. above the solvent boiling point. Fifth, the solvent containing the extract must be heated to 100.degree. C. above the solvent boiling point; therefore, reactive extracts are likely to decompose during the extraction process. Sixth, sequential solvent extraction is impossible on a single sample unless the sample is removed and reassembled in a second apparatus. Finally, the extraction solvent containing the extract must be quantitatively transferred from the tubular member and the solvent evaporated prior to gravimetric analysis.
Therefore, a need exists for a simple, inexpensive and versatile procedure for separating and extracting a wide variety of chemical mixtures for quantitative and qualitative analysis or identification.